1. Field of the Invention
The present invention relates to a user interface including a display device and a touch panel disposed on a screen of the display device.
2. Description of the Related Art
As a technique related to a user interface using a touch panel disposed on a screen of a display device, the following technique has been known. That is, a vibrator for vibrating a touch panel is provided, a user's operation of touching an area of the touch panel corresponding to a button displayed on a display device is accepted as a button touching operation, and a response to the touch operation is fed back to the user by using vibration of the touch panel (e.g., Patent Documents 1 and 2: Japanese Unexamined Patent Application Publication Nos. 2003-16502 and 2000-137576).
Also, as another technique related to a user interface using a touch panel disposed on a screen of a display device, the following technique has been known. That is, after a user has touched a touch panel, a button displayed in an area of a display device corresponding to the touched position just before a release operation (user's operation of releasing his/her finger from the touch panel) is accepted as a button decided by the user (e.g., Patent Documents 1 and 3: Japanese Unexamined Patent Application Publication Nos. 2003-16502 and 9-62446).
Furthermore, in these techniques, when the user performs touch and release operations on the touch panel, if the touched position just before the release operation is different from the position of the button corresponding to the touched position at the touch operation, selection of the released button is not accepted (e.g., Patent Document 3).
When the above-described known techniques of a user interface using a touch panel disposed on a screen of a display device are applied to, for example, a user interface of a vehicle-mounted system, the following problems arise.
In a vehicle-mounted system, relatively compact display device and touch panel are often used because of limited space, and thus the size of buttons displayed for accepting user operations are small in many cases. Further, a user has to operate a touch panel under an unstable environment while driving a car.
In another case, after a user has touched a position on a touch panel corresponding to a desired button, the user's finger on the position may be moved along the touch panel to another position corresponding to another button due to movement of a car. Therefore, as in Patent Document 1, when the operation of a button corresponding to a release position is unconditionally accepted, which means that a button operation is accepted against the user's intention.
On the other hand, a user's touch period during a button operation (period when the user keeps a button touched) is different depending on users. As the touch period is longer, the possibility that the touched position changes due to movement of a car increases. Therefore, as in Patent Document 3, if a button operation is unconditionally refused in a case where the touched position and released position are not at the position corresponding to the same button, a user who keeps a button touched for a long time cannot operate a desired button.
Further, when the above-described method is applied to a vehicle-mounted system, a user cannot always touch a proper position on the touch panel corresponding to a desired button due to the small size of the buttons and an unstable environment of a moving car.